Automotive alternators that use Lundell rotors have been used in automobiles for decades. Due to environmental issues in recent years, there is demand for idling reduction systems that stop an engine when a vehicle is stopped such as waiting at a traffic light. Idling reduction systems can be constructed without modifying engine layout significantly by using a conventional alternator as a generator-motor to start the engine after idling reduction. Automotive alternator-motors that are used in idling reduction systems are connected to the engine by means of a belt, and are required to rotate at rotational frequencies that are two to three times an engine rotational frequency. For this reason, pole cores have been produced using solid cores that are made of steel materials to increase the rigidity of the pole core. However, new problems have arisen such as eddy currents flowing through the pole core due to the pole core being produced using a solid core.
In consideration of these conditions, conventional automotive alternator-motors have been proposed in which surfaces of claw-shaped magnetic pole portions of a Lundell rotor are made uneven to reduce eddy currents flowing on the surfaces of the claw-shaped magnetic pole portions (see Patent Literature 1, for example).
Conventional bicycle generators have also been proposed that include: a tubular body that has permanent magnets that are disposed in an annular shape; two stator cores that have a disk portion and a plurality of magnetic pole pieces that extend axially from the disk portion, and that are disposed so as to be coaxial to the tubular body such that mutual magnetic pole pieces are adjacent; core yokes that are disposed between the two stator cores, and that are magnetically coupled to the two stator cores such that magnetic flux passes through axially; and a ring-shaped coil that is disposed around the core yokes, eddy currents being suppressed by disposing slits on the disk portions thereof to improve efficiency (see Patent Literature 2 through 5, for example).